Reed relay assembly employing both a permanent magnet and a saturable core



A1182 2, 1966 Yosl-n'rosm HosoKAwA ETAL 3.264.425

REED RELAY ASSEMBLY EMPLOYING BOTH A PERMANENT MAGNET AND SATURABLE'CORE Filed Aug. 18, 1964 EZE- li (bunnu'rucrarnup-.r

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:w w l z I United States Patent O 3,264,45 REED RELAY ASSEMBLY EMPLOYING BOTH A PERMANENT MAGNET AND A SATURA- BLE CORE Yoshitoshi Hosokawa and Hisaei Kikuchi, Tokyo, Japan,

assignors to Nippon Electric Company Limited, Minatoku, Tokyo, Japan Filed Aug. 18, 1964, Ser. No. 390,394 Claims priority, application Japan, Aug. 26, 1963, SaS/45,61@ 4 Claims. (Cl. 20G-87) The instant invention relates to switches and more particularly to reed relay switches utilizing permanent magnet means which is so designed as to prevent false operation thereof.

Magnetically operated switches find widespread use throughout a variety of applications. One particular type of such a magnetically operated switch is a reed relay. Such switches are by their nature a make contact type switch, where the utilization of a permanent, magnet means with the reed rel-ay switch is possible to provide a break type reed relay structure. However, such structures have limited use due to their ranges of undesirable false operation and/-or reoperation which may occur during the operation of such a switch.

The instant invention provides a reed relay structure utilizing a permanent magnet which is so designed as to prevent false operation of the structure.

In reed relay switches utilizing permanent magnets it is typical to provide a reed relay structure encased in a glass envelope in which the engaging reeds of the relay structure are normally biassed to the disengaged position. Permanent magnet means are positioned in close proximity to the glass envelope with the reed relay so as to magnetize the reed elements causing them to move to the engaged position. The glass envelope and permanent magnet members are surrounded by (or inserted into) coil means adapted for receiving an electric current. When the current flowing through the coil reaches a predetermined magnitude and is of a predetermined polarity the magnification of the reed elements due to the permanent magnet member is cancelled, and the switch moves to the open position. However, if the current magnitude is increased still further over the first predetermined level, the magnetization of the coil greatly exceeds the magnetization of the permanent :magnet member thereby causing the reed elements to again move to the closed or engaged position. This operation is commonly referred to as false operation of the reed relay switch assembly. Typically, the ratio between a false `operation excitation current value and a normal' operation excitation current value, which is normally referred to as the false operation margin, is a ratio of approximately 2 or 3 to l. Thus, in circuit applications where current variations of large magnitudes are present due to rush or transient current flow which may occur, false operation of the reed relay switch may thereby occur causing consequent false operation of the circuit.

The instant invention utilizes ,a reed relay switch assembly capable of providing a false operation margin of substantially infinity in ideal structures as well as in structures in which large variations in the quality of the circuit -may yoccur due to manufacturing procedures nevertheless being capable of providing a false operation margin or ratio of or more.

The instant invention is comprised of a reed relay switch assembly having cooperating reed elements with their engaging contact portions encased in a glass envelope. Permanent magnet means are positioned in close proximity to the glass envelope and provide a magnetization of strength and polarity capable of retaining the reed elements in the closed position.

3,264,425 Patented August 2, 1966 A saturable magnetic core having typical hysteresis characteristics is positioned adjacent the `glass envelope with the air gap in the saturable magnetic core being substantially in alignment with the engaging surfaces of the reed elements contained within the Iglass envelope of the assembly. The saturable magnetic core is provided with an excitation winding. When an excitation current of a predetermined magnitude is applied to the excitation windings the saturable core member generates a magnetic eld in the region -of the engaging surfaces of the reed elements so as to cancel the magnetization eifect of the permanent magnet member. The design of the circuit is such that this value will be close to the saturation value of the core. if, due to transient or rush current conditions or any other causes, the magnitude of excitation current in the saturable core winding greatly exceeds the value necessary to generate a magnetic field to cancel the effect of the permanent magnet, this will in no way effect the magnetic field generated by the saturable core since, due to the inherent and well-known characteristics of the saturable core, once the core has reached a saturation condition additional current introduced into the excitation winding for the core, regardless of its magnitude, will have no eifect whatsoever upon the magnetic iield generated by the core member. Thus, it is virtually impossible to initiate the occurrence of a false operation, either through accidental or deliberate operation of the reed relay assembly. Thus it can be seen that, with the provision of a saturable core member and accompanying excitation winding in place of the normal coil, employed in present day devices, the possibility of inducing false operation of the reed relay assembly is completely eliminated.

It is therefore one object of the instant invention to provide a novel switch means.

Another object of the instant invention is to provide novel switch means comprising a reed relay structure having means for eliminating the false operation of the switch means.

Still another object of the instant invention is to provide novel reed relay switch means utilizing permanent magnet means and having magnetic means for canceling the magnetization effect of the permanent magnet means which is so designed as to virtually eliminate possible false operation of the reed relay switch means.

Another object of the instant invention is to provide novel reed relay switch means utilizing permanent magnet means and saturable core means having an excitation winding which is so designed as to generate a magnetic field to cancel the magnetization effect of the permanent magnet and at the same time to prevent false operation of the reed relay switch means which may be caused due to the presence of an excitation current in the core Winding of improper magnitude.

These and other objects of the instant invention will become apparent when reading the accompanying description and drawings in which:

FIG. 1 shows a longitudinal sectional view of a conventional break type reed relay switch.

FIG. 2a shows a longitudinal sectional view of a reed relay switch assembly designed in accordance with the principles of the instant invention.

FIG. 2b shows an end View of the reed relay switch assembly of FIG. 2a.

FIG. 3 is a plot showing the magnetization characteristics of the assembly of FIGS. 2a and 2b provided for the purpose of illustrating the principles of the instant in- Ventron.

Referring now to the drawings, FIG. 1 shows a conventional reed relay assembly 10 having first and second reed relay switches 11 and 12. Each of said switches are comprised of a glass envelope 13 having first and second reed elements 14 and 15, the adjacent ends of lthe letters N and S, as shown in the figure.

which are positioned in an overlapping manner and the opposite ends of which protrude through the glass envelope 13 for connection with an electrical circuit (not shown). The reed elements 14 and 15 are formed of a substantially resilient conductive (i.e., metallic) material, and are normally ,biased so that their overlapping ends are out of engagement with one another in the manner shown in reed relay assembly 11. The region within each glass envelope 13 is typically a vacuum with the elements being hermetically sealed within t-he glass envelope.

The reed relay switch assemblies 11 and 12 are positioned in the manner shown in FIG. 1 and a rod shaped bar magnet 16 is positioned so as to be in close proximity with reed switch 12. Permanent magnet member 16 is magnetized with its north-south ends being designated by The bar magnet 16, being in close proximity to switch 12, acts upon the reed elements 14 and 15 of switch 12 to hold them into the closed position as shown. Due to the relative positioning between reed switch 11 and bar magnet 16, the magnetization has Very little effect upon reed elements 14 and 15 of switch 11 allowing them to remain in the open position.

Surrounding reed switches 11 and 12 and bar magnet 16, is a coil 17 adapted for receiving an excitation current at its input terminals 17a.

In the absence of an excitation current, the reed elements of treed switches 11 and 12 remain in the position as shown in FIG. l. When an excitation current is applied to the terminals 17a of coil 17 and reaches a predetermined current magnitude, magnetization of the reed switch 12 due to bar magnet 16 is canceled by the magnetization generated by coil 17 causing switch 12 to open while at the same time causing the reed switch 11 to close. If the excitation current is further increased in magnitude over this rst predetermined level, so that the magnetization of coil 17 exceeds the permanent magnetization of bar magnet 16 by a considerable amount, then the reed switch 12 which opened during normal operation is again closed with the result being the false operation referred to above. The ratio between the false operation excitation value of current and normal operation excitation value of current, which is commonly referred to as t-he false operation margin is a ratio applying in the range of 1:2 to 1:3. Result of this operation causes a reed switch assembly of the type shown in FIG. 1 to be unusuable in circuitry where wide variations in excitation current values or in circuits wherein in-rush current or transient current may be present to cause such a false operation.

In accordance with the instant invention, the utilization of a saturable core member coupled with the arrangement of the magnetic circuit which avoids the necessity for placing the permanent magnet and reed switches within a coil structure results in greatly simplified manufacturing procedures for the assembly of such switches, while at the same time providing substantially the same operation and providing false operation margins of substantially infinity and, even in `cases where large variations in quality control of circuit manufacture may occur, will still, nevertheless, result in false operation margins of 10 or greater.

Referring to FIGS. 2a and 2b there is shown therein a switch embodiment 20 of the instant invention Which is comprised of reed switches 21, 21 and 21l positioned in side by side arrangement with the glass envelopes of neighboring switches making physical contact with one another. A permanent magnet member 22 is so positioned that it rests upon the switch members 21 through 21 in the manner shown in the ligure and is magnetized with its north-south poles oriented in the manner designated by characters N and S.

A saturable core 23 having an air gap 24 is positioned along the underside of reed switches 21 through 21 such that the air gap 24 is substantially in alignment with the 4 opposing faces of the reed elements 14 and 15 of each reed switch 21 through 21". Bar magnet 22, saturable core 23 and reed switches 21 through 21" may be lixedly secured to one another so as to provide a substantially unied structure through the employment of suitable adhesive means so as to position and secure the members to one another in the manner shown in FIGS. 2a and 2b.

The saturable core member 23 is provided with an excitation winding 25 utilized for the purpose of controlling the saturable state of the core member 23.

When the excitation coil 25 is in the unexcited state, that is, when no current is passed through coil 25, the elements of the reed switches 21 through 21 are magnetized .by permanent magnet member 22, causing the elements to be in the engaged or closed position as can best be seen in FIG. 2a.

When an excitation current is introduced into winding 25 causing a magnetic field to be generated across the air gap 24, the magnetic potential difference between the opposing reed elements or contacts of the reed switches 21-21 decreases as a result of increase in magnetization due to the saturable core 23 ultimately causing the release of the reed switch elements moving them to the open position, which is the position occupied by the reed switch 11 of FIG. 1.

The design of the switch assembly in FIGS. 2a and 2b is such that the reed elements of switches 21 through 21" move to the open position at substantially the same time that the core member 23 reaches substantially its saturation state. Thus, any increase in magnitude of the excitation current introduced into winding 25 will have no elfect whatsoever upon the reed switches 21 through 21" since the saturable core 23 will have reached its saturation state and is thereby incapable of increasing the magnetic iield across its air gap 24. Consequently, there is no danger whatsoever of reoperation of switches 21 through 21 due to over-excitation of the saturable core member 23.

Referring now to FIG. 3, the principle of the invention will now be explained with reference to the curves shown therein. The .abscissa of the plot of FIG. 3 shows the excitation ampere-turns of the coil 25 plotted against the magnetic potential of the reed switches shown along the `ordinate of the plot of FIG. 3. When the excitation ampere-turns is zero, the magnetic potential in the region of reed switches 21 .through 21" is due exclusively to the magnetization value M of the permanent magnet member 22 causing the reed switches 21 through 21 to be in the closed position. With the application of excitation current in coil 25 in the positive direction along abscissa of the plot of FIG. 3, the magnetic potential decreases along the thick line curve 26. At the point a along curve 26 t-he reed switches 21 through 21" are released in which condition is maintained due to the fact that the core 23 reaches its saturation state at a point c which is just slightly ibelow the point a. With a decrease of excitation current the reed relay switches are restored to the closed position due to the magnetic potential of the permanent magnet member 22 as shown Iby the curve 27 with the magnetic potential being almost entirely due to lthe permanent magnet member at point b along curve 27 which represents the combined effects of the permanent magnet member 22 .and saturable core member 23 immediately before the excitation current in core 23 falls to zero.

It can thereby be seen that it is possible to simply and readily provide a reed relay structure employing a permanent magnet member in which false operation of the reed relay is virtually eliminated. By lamination of the saturable core 23 in order to lessen the eddy current in the core member this results in a reed relay having an advantage of a very short delay in operation time, providing a reed relay wherein the technical merits of the invention are remarkably augmented.

It should further be understood that by appropriate alteration of the switch assembly elements, it is possible to provide reed relay switch means which have reed elements which are normally enga-geable and having a permanent magnet means for magnetizing these elements out of engagement. The saturable core member is then energized into saturation for the purpose of offsetting the effect of the permanent magnet means to permit the reed elements to move to the engaged position. The permanent magnet at this time will be in t-he saturation state in the same manner as was previously described so as to prevent false operation of the reed relay switch means.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the append-ing claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are dened as follows:

1. Reed relay switch means including at least one reed relay switch comprised of irst and second conductive reed elements sealed within suitable housing means and normally -biased out of engagement; permanent magnet means positioned in close proximity to said housing and in the region of engagement of said reed ele-ments for holding said reed elements in the engaged position; saturable core means having an excitation winding which, when energized, drives said saturable core substantially into a saturation state; at least one portion of said saturable core being positioned adjacent said housing and in the region of engagement of said reed elements; said excitation winding being wound .about a second portion of said saturable core and 'being located a spaced distance from said housing, said saturable core generating a magnetic field of predetermined lield strength in said saturation state to oiset the effect of said permanent magnet means permitting said conductive reed elements to become disengaged; said saturable core preventing any appreciable increase in iield strength when in said saturation state thereby preventing false operation of said switch means.

2. Reed relay switch means including at least one reed relay switch comprised of first .and second conductive reed elements sealed within suitable housing means and normally biased into engagement; permanent magnet means positioned in close proximity to said housing and in the region of engagement of said reed elements for holding said reed elements in the disengaged position; saturable core means having an excitation winding which, w-hen energized, drives said saturable core substantially into .a saturation state; at least one portion of said saturable core being positioned adjacent said housing and in the region of engagement of said reed elements; said excitation winding being wound about a second portion of said saturable core and being located a spaced distance from said housing, said saturable core generating a magnetic field of predetermined field strength in said saturation state to offset the eiect of said permanent magnet means permitting said conductive reed elements to 'become engaged; said saturable core preventing any appreciable increase in eld strength when in said saturation state whereby preventing false operation of said switch means.

3. Reed relay switch means including at least one reed relay switch comprised of first and second conductive reed elements sealed within suitable housing means and normally biased out of engagement; permanent magnet means positioned in close proximity to said housing for holding said reed elements in the engaged position; saturable core means having an excitation winding which, when energized, drives said saturable core substantially into a saturation state; said saturable core generating a magnetic lie-ld of predetermined eld strength in said saturation state to offset the eiiect of said permanent magnet means permitting said conductive reed elements to become disengaged; said saturable core preventing any appreciable increase in eld strength when in said saturation state thereby preventing false operation of said switch means; said saturable core being a substantially solid magnetic core member having an air gap; said air gap being positioned adjacent said housing and in close proximity .to the region of engagement of said reed elements; said excitation winding being wound about said core a spaced distance from said housing.

4. Reed relay switch means including at least one reed relay switch comprised of iirst and second conductive reed elements sealed within suitable housing means and normally biased into engagement; permanent magnet means positioned in close proximity to said housing for holding said reed elements in the disengaged position; saturable core means having an excitation Winding which, when energized, drives said saturable core substantially into a saturation state; said saturable core generating a magnetic field of predetermined eld strength in said saturation state to offset the effect of said permanent magnet means permitting said conductive reed elements to become engaged; said saturable core preventing any appreciable increase in eld strength when in said saturation state thereby preventing false operation of said switch means; said saturable core Ibeing a substantially solid magnetic core member having an air gap; said air gap being positioned adjacent said housing and in close proximity to the region of engagement of said reed elements; said excitation winding being wound about said core a spaced distance from said housing.

References Cited by the Examiner UNITED STATES PATENTS 2,245,391 6/ 1941 Dickten 200-87 3,015,707 1/1962 Perreault 200-93 X FOREIGN PATENTS 906,554 9/ 1962 England. 938,131 10/ 1963 England.

BERNARD A. GILHEANY, Primary Examiner.

I. J. BAKER, Assistant Examiner. 

1. REED RELAY SWITCH MEANS INCLUDING AT LEAST ONE REED RELAY SWITCH COMPRISED OF FIRST AND SECOND CONDUCTIVE REED ELEMENTS SEALED WITHIN SUITABLE HOUSING MEANS AND NORMALLY BIASED OUT OF ENGAGEMENT; PERMANENT MAGNET MEANS POSITIONED IN CLOSE PROXIMITY TO SAID HOUSING AND IN THE REGION OF ENGAGEMENT OF SAID REED ELEMENTS FOR HOLDING SAID REED ELEMENTS IN THE ENGAGED POSITION; SATURABLE CORE MEANS HAVING AN EXCITATION WINDING WHICH, WHEN ENERGIZED, DRIVES SAID SATURABLE CORE SUBSTANTIALLY INTO A SATURATION STATE; AT LEAST ONE PORTION OF SAID SATURABLE CORE BEING POSITIONED ADJACENT SAID HOUSING AND IN THE REGION OF ENGAGEMENT OF SAID REED ELEMENTS; SAID EXCITATION WINDING BEING WOUND ABOUT A SECOND PORTION OF SAID SATURABLE CORE AND BEING LOCATED A SPACED DISTANCE FROM SAID HOUSING, SAID SATURABLE CORE GENERATING A MAGNETIC FIELD OF PREDETERMINED FIELD STRENGTH IN SAID SATURATION STATE TO OFFSET THE EFFECT OF SAID PERMANENT MAGNET MEANS PERMITTING SAID CONDUCTIVE REED ELEMENTS TO BECOME DISENGAGED; SAID SATURABLE CORE PREVENTING ANY APPRECIABLE INCREASE IN FIELD STRENGTH WHEN IN SAID SATURATION STATE THEREBY PREVENTING FALSE OPERATION OF SAID SWITCH MEANS. 